Photothermal Catalytic Depolymerization and Glycolytic Regeneration of Polyethylene Terephthalate

The efficient recycling of polyethylene terephthalate (PET) waste is essential for sustainable development, owing to the extensive utilization of this plastic in daily life. However, the high depolymerization energy barrier inherent to conventional single thermal catalytic technology constrains its reaction efficiency, necessitating substantial external heat input and energy consumption. Recently, photothermal synergistic catalysis has emerged as one of the most promising methods for PET glycolysis regeneration, with its core lying in the photothermal conversion and catalytic mechanism. In this review, the core mechanisms and recent advances in the photothermal catalytic depolymerization of PET to bis(2-hydroxyethyl) terephthalate (BHET) are systematically discussed. First, this review elucidates the critical role of photothermal conversion in PET recycling based on the structural characteristics of PET and the thermodynamic and kinetic principles governing its depolymerization. Particular emphasis is placed on how photothermal synergistic catalysis significantly lowers the depolymerization energy barrier and enhances reaction efficiency. Subsequently, the depolymerization mechanism of PET is analyzed in detail, with a focus on the synergistic promotion by catalyst active sites of electrophilicity of carbonyl groups in PET ester bonds and the nucleophilicity of the hydroxyl oxygen in ethylene glycol (EG), thereby achieving efficient transesterification.